DC circuit laboratory
Experiment No. 6
Delta – Star connection
Aim of experiment: To study the properties of delta-star connection.
Apparatus
1. DC circuit training system
2. Set of wires.
3. DC Power supply
4. Digital A.V.O. meter
Theory
In solving networks (having considerable number of branches) by the
application of Kirchhoff's Laws, one sometimes experiences great difficulty
due to a large number of simultaneous equation that have to be solve.
However, such complicated networks can simplify by successively replacing
delta meshes by equivalent star systems and vice versa.
1
1
R12
R13
R1
R3
2
R23
R2
3
2
3
Star-connection
(a)
Delta-connection
(b)
Fig (1)
DC circuit laboratory
Suppose we are given three resistance R12,R23 and R13 connected in delta
fashion between terminals 1,2 and 3 as in Fig.(1-a). So far as the respective
terminals are concerned, these given three resistances can be replaced by the
three resistances R1, R2 and R3 connected in star as shown in Fig.(1-b). These
two arrangements will be electrically equivalent if the resistance as measured
between any pair of terminals is the same in both arrangements.
1. To convert from delta connection to star connection
R1 
R 12  R 13
R 12  R 23  R 13
R2 
R 12  R 23
R 12  R 23  R 13
R3 
R 23  R 13
R 12  R 23  R 13
2. To convert from star connection to delta connection
R12  R 1  R 2 
R1  R 2
R3
R 23  R 2  R 3 
R3  R2
R1
R 13  R 1  R 3 
R 3  R1
R2
Procedure
1. Using the DC circuit trainer, connect the circuit shown below.
2. Measure "I1, I2, I3 " practically.
3. Record your results in the table below
4. By using delta-star conversion, find the star resistance R1, R2, R3
theoretically.
DC circuit laboratory
50
I1
A
20
20
A
5V
I2
5V
40
A
I3
5. Using the DC circuit trainer, connect the circuit shown below:
20
20
A
40
I1
A
5V
5V
A
I2
I3
DC circuit laboratory
6. Measure "I1, I2, I3 " practically.
7. Record your results in the table below
I1
I2
I3
Delta connection
Star connection
8. Connect circuit the circuit shown in Figure below and measured the
equivalent resistance between any two terminals "1-2, 2-3, 1-3" by using
AVO meter.
50
20
20
1
2
100
40
100
3
3
9. Using the DC circuit trainer, Connect circuit the circuit shown in Figure
below and measured the equivalent resistance between any two terminals "12, 2-3, 1-3" by using AVO meter.
DC circuit laboratory
1
50
2
100
100
3
3
Discussion
1. Comment on your results.
2. Compare between the practical and theoretical results.
3. Comment on step 8 and step 9
4. Find IT and RT for the circuit below
IT
1.5Ω
8v
5Ω
5Ω
10Ω
2Ω
3Ω
RT
2Ω
3Ω
3Ω